Poor white line markings on some of the most dangerous roads in the UK could be contributing to the number of serious road accidents, a safety group says.
The Road Safety Markings Association (RSMA) said half the markings on eight roads in Yorkshire, Lancashire and Sussex fell below minimum standards.
The organisation said it had found evidence of badly-worn lines, and in some cases none at all.
The roads were earlier identified as among the most dangerous in the UK.
The RSMA said a five-mile section of the A6135 north of Sheffield had the poorest road marking in the survey, with 75% of markings non-existent or highly worn.
George Lee, national director of the RSMA, said: "This report flags up some serious concerns for the overall conditions of our road network.
"The failure to maintain road markings may be a contributory factor to the number of fatal and serious accidents on these roads."
He added that improvement work had been carried out on some of the roads, which were among 10 named by the Road Safety Foundation (RSF) earlier this year as the most dangerous in the UK.
The RSF mapped and measured the safety of 27,960 miles (45,000km) of motorways and A roads in Britain.
A West Sussex County Council spokeswoman said they had carried out three separate surfacing schemes on the A281 this year.
She added: "This has resulted in approximately 75% of the road markings along this nine-mile section being replaced. The remaining markings are scheduled for replacement in the next financial year."
Lancashire County Council member Tim Ashton, who is responsible for highways and transport, said improving road safety was "a real priority".
"This report is based on data from 2006 to 2008 and we have carried out maintenance work since that time to improve road safety," he said.
"A study is currently being carried out on the A581 between Croston and the A59 to identify areas where safety could be improved."
Road safety minister Mike Penning said: "Britain has one of the best road safety records in the world and local road improvement projects have undoubtedly contributed to this.
"All the evidence suggests that hundreds of lives are saved each year because of safety improvements to roads themselves.
"Simple measures - such as good road markings - can make a massive difference and I urge local authorities to consider these carefully as they continue to strive to reduce deaths and injuries on their roads."